pcmhacking.net

Ive been absent from this site for a long time.

There is a thread floating around about my turbo fiat 131 that I built a few years ago and was tuned by Festy on this forum. That car was a great success but made too much power for the other pieces of the drive line.

After destroying 3 diffs and one gear box (all from hard acceleration - never did burnouts in it) I was over it. The turbo manifolds and accessories were sold off and a new NA engine was built using all the parts of the turbo engine except for new high comp pistons and larger / longer duration intake and exhaust cams, a set of extractors and twin dellorto DHLA 45’s - More than one person said I was crazy for going from efi turbo to n/a carbs.

Needless to say I was and still am very happy with the new layout, car is less refined now that its carburetted but it sounds better and frankly more fun to drive. I do miss that boost sometimes though.

Anyway, reason for my long-winded post is I still have the computer & loom, fuel pump and surge tank, ignition module / coils, crank pully & trigger etc and was thinking about doing a budget ITB conversion.

I can easily hook up the wiring loom and computer, fuel pump etc. I can build an intake manifold from steel that will mount up some CBR1000 throttle bodies (44mm)

I understand some of the issues with tuning ITBs involve weak vacuum reference for MAP sensor etc but know there are ways around this by way of tuning with TPS and engine speed (alpha N?)

How realistic an endeavour will it be to get the engine running well on ITBS with a Delco computer?
Have many people attempted it? Ive done a search and have only found a single topic with someone who’s mounted itbs on a holden 6.

Thanks, Andrew

I would also like to see this done to verify that the experimental alpha N mode works and is tunable. From what I have been told ITB EFI is actually easier to tune at low rpm and idle than a traditional manifold with much better idle quality but it does need alpha N to work.

Theres been plenty of people ask about it, but i have never heard results of anyone doing it, so that either means they never did, never got it to work properly or just never shared after they got it working.

like vlad said, it should work, the code is there to do it, just cant verify it in the real world.

Are you guys sure of this? I have looked and maybe I missed it but I dont see a flag or option for TPS as load. I thought this was the one thing that kalmaker street pro 3 had that 12p didnt.

It's got an Alpha N flag. I think it forces the ECU to use the default map mode which is what it uses when the MAP fails and uses the TPS as the input instead.

I have tried this fail safe before on my VP, un-pluged the MAP and the engine ran fine from what I could tell when free revving it but I didn't actually drive it.

I believe it works by using a model to extrapolated MAP values based on the TPS and other engine conditions.

Oh yeah there it is. "Map A: set= Use MAP For Load Variable. Clear Use Default MAP (Alpha-N)"

I tested this today in my VP. Started and ran fine, slight roughness in a few points in the rpm range when free revving for about 20-30 sec after starting but it cleared up fine. Drove the car like this and it drove 99% normal like nothing happened. Only thing I noticed is the decel fuel cut and injector cut in had a slight hysteresis at very low TPS values (at a guess 2% or less).

I think there might be an adjustment for that somewhere but alpha N looks very promising. I'd say with ITBs go for it. I think it will work great when tuned properly.